Voice enhancement system and method

ABSTRACT

A telecommunications network (120) is provided with adaptive gain control (AGC) of the voice signals in network (120). Network (120)includes an input (12) for receiving a voice signal, an output (14) for receiving the voice signal, and a coupling between input (12) and output (14) including at least one switch (124) or (126). Network (120) also includes voice enhancer (10) including power averager (18) for measuring and determining the average power of an input signal. Voice enhancer (10) also includes bass band equalizer (16) to attenuate a predetermined portion of the input signal to provide an equalized input signal. From the average power of the input signal is determined a scaling factor from a gain/attenuation look-up table (28). Voice enhancer (10) also includes output scaler (30) coupled to output (14), output scaler (30) scales the equalized input signal with the scaling factor and provides the scaled signal to output (14). Voice enhancer (10) also includes bass to treble power comparator (20) for detecting tandem enhancement and voice-band data detector (22) which cause enhancer (10) to be disabled appropriately.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 08/161,120, filed Dec. 2, 1993 and entitled "Voice EnhancementSystem and Method," now U.S. Pat. No. 5,471,527.

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to the field of voice signalprocessing in a telecommunications network, and more particularly to animproved method and apparatus for enhancing the quality of voice signalsin a telecommunications network.

BACKGROUND OF THE INVENTION

Modern telecommunications networks are comprised of input and outputdevices, e.g., telephone sets, local central offices, and one or moretelephone switches which are used for processing voice signals in thenetwork. Voice signals can be characterized as containing two regions,including the bass region and the treble region. The bass region istypically considered to be that part of the voice signal below 300 hertz(Hz), and the treble portion is that part of the signal above 300 Hz.Voice signals may be attenuated in the bass band region by one or moreof the elements in a telecommunication network.

The Electronic Industry Association (EIA) standard RS-470, publishedJanuary 1981, recommends that the input voice signal be attenuated belowapproximately 300 Hz by the codec in the input telephone station. Thisattenuation of the amplitude of the bass portion of the input voicesignal is recommended because background noises in a telecommunicationnetwork lie in the bass region. By decreasing the amplitude of the bassportion of the input signal, the background noises of the network arealso diminished.

Additionally, central offices of a telecommunication network may alsoattenuate the bass band region of a voice signal. Within a centraloffice may be located a channel bank which converts the analog inputvoice signal to its digital equivalent. The digital voice signal iscoupled to the receiving telephone set by a digital telephone switch orswitches. Before the signal is provided to the receiving telephone set,it is converted back to analog format at another central office locatedbetween the last switch and the receiving telephone set. A channel bankmay attenuate the bass portion of the input voice signal during theanalog to digital conversion process.

Some networks, therefore, attenuate the bass region of the input voicesignal twice; in the input telephone set and in the central office.Attenuation of the bass region of the input signal results in a voicesignal at the receiving telephone set that is not a true representationof the speaker's voice. Techniques have thus been proposed to compensatefor the loss of bass in a telephone speaker's voice.

One prior approach for providing an enhanced voice signal in atelecommunications network utilizes a fixed gain technique. In the fixedgain approach, the bass portion of the voice signal is amplified whilethe signal is in the telecommunications network and before it issupplied to the receiving telephone set. This approach compensates forattenuation of the input signal with a fixed gain at some point withinthe network. This approach also amplifies the previously noted networkbackground noises within the bass band region.

Moreover, if the input voice signal is a loud signal, i.e., the speakeris speaking at a high decibel (dB) level, the fixed gain enhancementapproach will further amplify the high decibel signal, thus resulting ina signal at the receiving telephone set which can be uncomfortable tolisten to. Alternatively, applying a fixed gain to a high decibel inputsignal can result in over-driving/saturating different network elements,making the signal less clear than it would have been if the fixed gainhad not been applied.

An additional problem associated with the fixed gain technique for voiceenhancement occurs when data is transmitted over the telecommunicationsnetwork in the voice-band. This is becoming a more frequent occurrencefor telecommunications systems as the use of facsimile machines andmodems coupling computers continues to grow. A modem or facsimilemachine transmits voice-band data at a high amplitude and at ahigh-frequency, e.g., 2700 Hz. Therefore, should the fixed gaintechnique be applied to a voice-band data signal, it will beunnecessarily amplified, thus resulting in a voice-band data signal thatis difficult to use on the receiving end.

Detectors for sensing the transmission of voice-band data have beenemployed to solve the problems associated with voice-band datatransmissions. These detectors are remote to the fixed gain enhancementcircuitry, requiring an external control link to the enhancementcircuitry for disabling the circuitry. This ensures that the voice-banddata is not amplified.

Another problem associated with previously developed voice enhancementsystems occurs when an input voice signal travelling in atelecommunications network encounters or must pass through multiplenetwork elements (tandem network) that include fixed gain voiceenhancement circuitry. Current fixed gain voice enhancement systemscannot detect when a input voice signal has already been adjusted by thefixed gain technique. Therefore, a voice signal amplified in a firstelement of a tandem network may be subsequently again amplified by thesecond element in the network. This additional amplification can resultin the saturation of the voice signal, or at a minimum, make the signaluncomfortable to listen to on the receiving telephone set. Also,multiple enhancements to a voice signal can result in oscillation of thevoice signal in the tandem network.

SUMMARY OF THE INVENTION

Therefore, a need has arisen for a voice enhancement system whicheliminates the problems associated with prior voice enhancement systems.

A need exists for a voice enhancement system which does not amplify thebackground noise of the telecommunications network during periods ofsilence on the network.

A need further exists for a voice enhancement system that does notamplify higher level voice signals.

An additional need exists for a voice enhancement system that will notover-drive or saturate higher level voice signals.

A need exists further for a voice enhancement system that detects thetransmission of voice-band data without requiring a separate externaldetector.

A further need exists for a voice enhancement system that workseffectively in a tandem network.

An additional need exists for a voice enhancement system that does notcause oscillation of the voice signal.

Therefore, one aspect of the present voice enhancement system preventsthe amplification of background noise during periods of silence on thenetwork call.

Another aspect of the present system adaptively changes theamplification of the voice signal so that voice signals of sufficientstrength are not amplified.

An additional aspect of the present system ensures that high level voicesignals are not over-driven or saturated.

Another aspect of the present invention is that it internally detectsthe transmission of voice-band data and disables signal enhancementappropriately.

An additional aspect of the voice enhancement system of the presentinvention is that it can successfully be employed in a tandem network.

Yet another aspect of the present system is that it minimizesopportunity for causing oscillation of the voice signal.

In accordance with the present invention, a voice enhancement system isprovided which substantially eliminates or reduces disadvantages andproblems associated with prior fixed gain enhancement systems.

A system including the adaptive gain control voice enhancer of thepresent invention includes an input for accepting voice signals and anoutput for receiving voice signals with a coupling between the input andoutput. The coupling includes a voice enhancer which contains a poweraverager for determining the average power of the voice signal. Thevoice enhancer also includes an equalizer for attenuating apredetermined portion of the voice signal and an output scaler forscaling the equalized voice signal in response to the determined averagepower and providing the scaled signal to the output.

Specifically, the voice enhancer of the present invention includes avoice-band data detector and a tandem voice enhancement detector, eitherof which can disable the voice enhancer appropriately.

A method for providing adaptive gain control with the voice enhancer ofthe present invention includes determining the average power of an inputvoice signal, and determining a scaling factor in response to theaverage power of the input signal. The present inventive method alsoincludes equalizing the input voice signal by attenuating apredetermined portion of the input voice signal. The present methodincludes scaling the equalized input signal with the determined scalingfactor and coupling the scaled voice signal to an output.

More specifically, the present method for providing adaptive gaincontrol voice enhancement includes decoupling the scaled voice signalfrom the output upon detecting voice-band data or tandem enhancement.

A technical advantage of the adaptive gain control (AGC) voiceenhancement system of the present invention is that it provides anenhanced voice signal which sounds more like the speaker's voice. Thepresent adaptive gain control voice enhancement system is compatiblewith either voice signals or voice-band data signals being transmittedin a telecommunications network.

The present voice enhancement system also provides a technical advantageof eliminating problems associated with currently available fixed gaincontrol voice enhancement systems. The adaptive gain control of thepresent system attenuates high level input voice signals and amplifieslow level input voice signals. The present invention will, therefore,not saturate an input voice signal that is initially at a high level.

An additional technical advantage of the present adaptive gain controlvoice enhancement system is that it will not amplify periods of silencein a ongoing conversation between remote telephone sets. Therefore, thepresent system will not amplify network background noise when voicesignals are not being transmitted.

Another technical advantage of the present invention is that it iscapable of detecting in a tandem network a voice signal which has beenpreviously enhanced. Upon detecting a tandem configuration, the presentsystem disables itself so that a previously enhanced signal is not againamplified. This provides a technical advantage of preventing anoscillation condition of a signal in the network.

Yet another technical advantage of the present system is that it iscapable of detecting the transmission of voice-band data and disablingthe adaptive gain of the signal as required. The present invention isalso self-disabling upon detection of a tandem network or voice-banddata and does not require an external control link or detector.

An additional technical advantage of the present invention is that itcan be implemented in existing telecommunications equipment, for examplein the echo canceller of a network, the present system is alsocompatible with existing telecommunication networks.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention andadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings in which likereference numbers indicate like features and wherein:

FIG. 1 illustrates a block diagram of the adaptive gain controlcircuitry of the voice enhancement system of the present invention;

FIG. 2 shows a representative flow chart of the steps executed by theadaptive gain control circuitry for voice enhancement;

FIGS. 3a through 3d illustrate representative voice signals at differentstages of the adaptive gain control process of the present invention;

FIG. 4 is a block diagram depicting a possible location of the voiceenhancement system of the present invention within a telecommunicationnetwork; and

FIG. 5 is a block diagram of a telecommunications network incorporatingthe adaptive gain control system for voice enhancement of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are illustrated in the FIGURES,like numerals being used to refer to like and corresponding parts of thevarious drawings.

FIG. 1 illustrates a block diagram for implementing the adaptive gaincontrol (AGC) voice enhancement system of the present invention. Voiceenhancer 10 of the present invention is coupled to an input 12 and anoutput 14. Input 12 is typically any device which would provide an inputvoice signal from a telephone set. Output 14, likewise includes anydevice used to produce an output voice signal to a telephone set.

Input 12 is coupled in parallel to a bass band equalizer 16, poweraverager 18, bass to treble power comparator 20, and voice-band datadetector 22 on the input side of voice enhancer 10. Bass band equalizer16 (or equalizer) equalizes an input voice signal by attenuating theamplitude of the treble portion of the input signal. Bass band equalizer16 can be embodied in a digital filter which decreases the amplitude ofthe treble portion of an input voice signal. A typical demarcationbetween the bass and treble regions of the input voice signal isapproximately 300 Hz, though other demarcations are possible withoutdeviating from the inventive concepts of the present invention. Bassband equalizer 16 essentially equalizes the bass band distortion of theinput signal introduced by an input telephone set and/or from analog todigital conversion of the signal in the channel bank of a centraloffice.

Power averager 18 of voice enhancer 10 measures the average power of aninput signal. This is accomplished with a variety of methods, and oneembodiment of power averager 18 is a low pass filter through which therectified input signal from input 12 is passed.

Also included in the input side of voice enhancer 10 is a tandem voiceenhancement detector or bass to treble power comparator 20. Bass totreble power comparator 20 detects potential tandem enhancement of aninput signal within a telecommunications network. Bass to treble powercomparator 20 continually monitors the ratio of bass to treble power ofthe input signal. It is known that for an average input signal, the bassto treble power ratio is generally within a predetermined range. It isalso known that the input telephone set and channel bank of a centraloffice in a network attenuate the bass signal, thereby decreasing thisratio. Bass to treble power comparator 20 continuously monitors thisratio in the input signal. If the monitored bass to treble power ratiois much lower than expected for an enhanced signal then bass to treblepower comparator 20 discerns that no tandem enhancement circuit ispresent. Conversely, if the monitored power ratio is comparable orhigher than expected, then bass to treble power comparator 20 discernsthat a tandem voice enhancement circuit is present. Bass to treble powercomparator 20 provides a technical advantage of detecting when an inputvoice signal has been previously enhanced so that voice enhancer 10 canbe used in tandem networks.

Voice-band data detector 22 also analyzes the input signal. Voice-banddata detector 22 determines whether the input voice signal is voice-banddata. Voice-band data detection methods are well known in the art andwill not be elaborated here. Voice enhancer 10 incorporates one of theprior art methods of detection so that the adaptive gain control of theinput signal can be disabled when voice-band data is detected.Voice-band data detector 22 provides a technical advantage of detectingthe transmission of voice-band data internally to voice enhancer 10without requiring external control links and detectors.

Coupled to bass to treble power comparator 20 and voice-band datadetector 22 is AGC enhancement disable 24. Based on the inputs of bassto treble power comparator 20 and voice-band data detector 22, AGCenhancement disable 24 determines whether voice enhancer 10 should bedisabled by switch 26. The default position of switch 26 enables voiceenhancement of the input signal, and will be disabled when AGCenhancement disable 24 determines that either the input signal has beenpreviously enhanced or that the input signal is voice-band data.

Gain/attenuation look-up table 28 is coupled to power averager 18. Oncethe average power of an input signal is determined at power averager 18,a signal representative of the average power is sent to gain/attenuationlook-up table 28. Gain/attenuation look-up table 28 contains scalingfactors that are applied to the input voice signal within the inventiveconcepts of the present invention. Gain/attenuation look-up table 28 isorganized such that if the average power of the input signal is high,then the corresponding scaling factor is low. This provides a technicaladvantage of preventing the over-amplification of high level signals andprevents over-driving or saturating the signal.

The scaling factor can be less than unity if the average power of theinput signal is sufficiently high. If the average power of the inputsignal is measured to be low, then the corresponding scaling factor ishigh. A typical input signal at average input power would have acorresponding scaling factor which provides minimal gain or attenuationof the signal, thereby ensuring that all signals receive AGC. Adaptivelychanging the scaling factor provides a technical advantage of preventingoscillation of the voice signal.

Output scaler 30 is coupled to gain/attenuation look-up table 28. Outputscaler 30 is also coupled to bass band equalizer 16 which provides theequalized input signal to output scaler 30. Output scaler 30 applies thepreviously determined scaling factor from gain/attenuation look-up table28 to accordingly amplify or attenuate the equalized input signal.Output scaler 30 provides the amplified signal to output 14.

Also shown in FIG. 1 is transparent path 32. Transparent path 32 iscoupled to input 12 and enhancement disable position 34 of switch 26.Variable attenuator 36 is located between the ends of transparent path32. Variable attenuator 36 can be included in voice enhancer 10 toprovide enhanced noise suppression when voice enhancer 10 detectssilence at input 12. When silence is detected, switch 26 is placed atenhancement disable position 34, and the path between input 12 andoutput 14 is by transparent path 32.

Upon switching to transparent path 32, variable attenuator 36 is set forminimum attenuation. Over a period of time each signal below the voicethreshold causes the attenuation in variable attenuator 36 to increase(for example, 0.5 decibels per 3 milliseconds) toward a maximum valuefor variable attenuator 36. Increasing the attenuation of variableattenuator 36 causes the background noises of the network to besuppressed. This provides the technical advantage of minimizing thelevel of background noises during periods of silence.

As the level of the input signals increase, the attenuation of variableattenuator 36 decreases towards minimum attenuation. After a shortperiod of integration (for example, 3 samples of the input signal) ofinput signals above the predetermined threshold, switch 26 moves back toits default position allowing for adaptive gain control of the inputsignals. Variable attenuator 36 is then reset to minimum attenuation.

It is noted that the functional blocks depicted in FIG. 1 may beembodied in separate discrete devices or in a single integrated circuitwithout departing from the inventive concepts of the present invention.Additionally, it is noted that the functional blocks depicted in FIG. 1may be implemented in whole or in part in software as well as inhardware.

The operation of voice enhancer 10 of FIG. 1 will be discussed inconnection with the flowchart of FIG. 2 and the representative signalsof FIGS. 3a through 3d.

FIG. 2 depicts representative steps executed by voice enhancer 10 of thepresent invention for AGC of an input voice signal. The flow begins atstep 50, and at step 52, the present voice enhancement process isinitiated when an input signal greater than a predetermined threshold isdetected. Below the predetermined threshold silence is declared to existon input 12, and switch 26 of voice enhancer 10 is placed in enhancementdisable position 34. An example for the predetermined threshold is 0.40dBm0, but it can also be adaptively changed based on quiescent noiselevels in the network or on the power level of the input voice signal.When silence is detected and switch 26 is placed in enhancement disableposition 34, the input signal is provided to output 14 without scaling.This provides the technical advantage of preventing the amplification ofnetwork background noise during periods of silence. Any of the blocksassociated with the input side of voice enhancer 10 (bass band equalizer16, power averager 18, bass to treble power comparator 20, or voice-banddata detector 22) can be used for detection of silence and an inputvoice signal.

Upon the detection of an input signal, a frame count is initiated atstep 54. A frame system is used by voice enhancer 10 to divide up thetransmission of signals into periods of time. A typical frame periodused in voice enhancer 10 correspond to 3 milliseconds.

Once an input voice signal has been detected at input 12, then at step56 voice enhancer 10 determines whether the input signal has beenpreviously enhanced. As described in conjunction with FIG. 1 above, foran average speech signal, the bass to treble power ratio is roughlywithin a predetermined range. At step 56, bass to treble powercomparator 20 measures the bass to treble power ratio to determinewhether it is consistent with a previously enhanced signal indicatingthat a tandem configuration exists. At step 58 a decision is made as towhether the tandem enhancement is present. If a tandem enhancement ispresent, then the flow proceeds to step 60 where AGC voice enhancementis disabled by AGC enhancement disable 24 by sending an appropriatesignal to switch 26 or its equivalent so that switch 26 will be moved toits enhancement disable position 34 (See FIG. 1). Since switch 26 ispreset at a default position enabling voice enhancement, then if atandem configuration is not detected at step 58, the flow proceeds tostep 62.

At step 62 the presence of voice-band data is detected. Voice-band datadetector 22 implements well-known voice-band data detection methodswhich need not be discussed in detail. At step 64 a query is made as towhether voice-band data is present in the input signal. If voice-banddata detector 22 senses the transmission of voice-band data at input 12,then at step 64 it sends an appropriate signal to AGC enhancementdisable 24, which causes switch 26 or its equivalent to move toenhancement disable position 34 at step 60. If voice-band data is notpresent at step 64, then the flow proceeds to step 66.

It is noted that a detection of a tandem configuration by measuring thebass to treble power ratio at step 56, and the detection of thetransmission of voice-band data at step 62, can occur eithersimultaneously or in reverse order to that which is depicted in FIG. 2.It is also noted that the default position of switch 26 or itsequivalent is to enable voice signal enhancement with the inventiveconcepts of the present invention. Upon detection of a previouslyenhanced signal or voice-band data will voice enhancement circuitry 10be disabled at switch 26.

At step 66, power averager 18 measures the power of the input signal,and at step 68, the power averager 18 determines the average power ofthe input signal. At step 70, power averager 18 sends a signalrepresentative of the measured averaged power to gain/attenuationlook-up table 28. At step 70, gain/attenuation look-up table 28 providesa gain/attenuation factor or scaling factor based on the measuredaverage input power. The scaling factor is related to the measuredaverage power as previously described, wherein an input signal with ahigh average power corresponds to a low or attenuating scaling factor,and a low level input signal corresponds to an amplifying scalingfactor. At step 72, bass band equalizer 16 equalizes the input voicesignal.

FIG. 3a shows an example of a representative input voice signal. X-axis100 is the frequency of the input signal, and Y axis 102 is theamplitude of the input signal in decibels (dB). Input signal 104 hasassociated with it a bass region 106 and treble region 108. Typicallythe demarcation between bass region 106 and treble region 108 is viewedas being 300 Hz on line 109, although other demarcation lines may besuitable. Bass region 106 of input signal 104 has been attenuatedrelative to treble region 108 by either or both an input telephone setand the channel bank of a central office .

FIG. 3b illustrates transfer function 110 applied by bass band equalizer16 in step 72 to equalize input signal 104. It is noted that transfersignal 110 decreases the amplitude of treble portion 108 of the inputsignal relative to bass region 106 of input signal 104.

FIG. 3c depicts equalized signal 113 which is signal 104 followingequalization at step 72 in bass band equalizer 16. Followingequalization in bass band equalizer 16 by transfer function 110,equalized signal 113 has a relatively flat amplitude over the entirefrequency range of the signal. It is noted that the determination of thescaling factor at step 70 and the equalization of the input signal atstep 72 can occur simultaneously or in the reverse order to thatdepicted in FIG. 2.

The flow then proceeds to step 74 where scaling of the equalized signal113 occurs. Output scaler 30 applies the scaling factor to equalizedsignal 113.

FIG. 3d illustrates two representative scaled output signals, whereinsignal 114 shows equalized signal 113 following a positive or amplifyingscaling factor, and signal 116 represents equalized signal 113 followinga negative or attenuating scaling factor.

Following the application of the scaling factor to the input signal, theprocess proceeds to frame counter step 76. To avoid changing scalingfactors too quickly, the scaling factor is adjusted every N frames witha maximum change of X dB, wherein for example, N could be 24 whichcorresponds to 3 milliseconds and X could be 0.5 dB. Therefore, theframe counter is incremented at step 76, and at step 78 it is determinedwhether a number of frames have passed which exceed N. If they have not,then the flow returns to step 74 where the same scaling factorpreviously determined is applied to the input signal until the framecount exceeds N. At step 78, if the number of frames exceeds N, the flowreturns to step 52 where the entire process is begun again. Thisprevents a scaling factor from changing too quickly.

It is noted that the flow of FIG. 2 allows for continuous adaptive gaincontrol (AGC) of the input signal. The scaling factor is redeterminedevery N frames of signal transmission allowing for changing the gain ofthe input signal as the input signal changes. It is also noted thatmethodology described in association with FIGS. 2 and 3a-3d isrepresentative of a possible embodiment of the present invention, andthat other embodiments are possible without departing from the inventiveconcepts of the present invention.

FIG. 4 shows a block diagram of an embodiment of voice enhancer 10 inecho canceller network element 80 in a typical telecommunicationsnetwork. An example of echo canceller network element 80 is EC24 echocanceller manufactured and sold by DSC Communications Corporation. Voiceenhancer 10 is shown in echo canceller network element 80 coupled tolong haul input 86, which provides the input voice signals beingprocessed in echo canceller network element 80. Voice enhancer 10performs the necessary AGC scaling of the input voice signal asdescribed in conjunction with FIGS. 1 through 3d above, and provides ontail out 88 the enhanced signals to hybrid 90. Hybrid 90 is coupled bytail in 92 to echo canceller adaptive filter 82 through summingcircuitry 84. Summing circuitry 84 provides the output signals to longhaul output 94. The operation of echo canceller element 80 to eliminateechoing effects in a two-way transmission line are well known in the artand will not be discussed herein. It is also noted that voice enhancer10 does not have to be placed in echo canceller network element 80 asother elements within a telecommunications network are suitablelocations for voice enhancer 10. It is noted that echo canceller networkelement 80 including voice enhancer 10 may be located in or separatelyfrom a telephone switch.

FIG. 5 shows telecommunications network 120 which is an example of anetwork which may incorporate the AGC voice enhancement system of thepresent invention to provide an improved voice signal transmission frominput 12 to output 14. Input 12 includes an input telephone set which iscoupled to central office 122. Central office 122 converts the analogvoice signals to digital signals in a channel bank. Central office 122provides coupling to telephone switch 124. Switch 124 is coupled to echocanceller network element 80 where voice enhancer 10 is included. Echocanceller element 80 is coupled to switch 126 and possibly others.Switch 126 shows an embodiment where echo canceller network element 81,including voice enhancer 10, is located within the switch rather thanexternal to it. Either location of voice enhancer 10 can be employedwithout departing from its inventive concepts. Switch 126 is coupled tocentral office 128 which in turn provides coupling to output 14. Thefunctionality of AGC voice enhancer 10 in echo cancellers 80 and 81 ofnetwork 120 is as previously described. It is noted that input 12 andoutput 14 will change roles as the telephone conversation progresses,thereby providing a two-way communication link between input 12 andoutput 14. It is noted that the embodiment of voice enhancer 10 in echocanceller network elements 80 and 81 is by way of an example oflocations for voice enhancer 10 of the present invention.

In operation of voice enhancer 10 of the present invention, an inputvoice signal is received on input 12. Bass band equalizer 16 equalizesthe input signal by attenuating the treble portion of the input signal.This essentially equalizes the signal which has previously had its bassregion attenuated by various elements of the network. Power averager 18measures and determines the average power of the input signal.Gain/attenuation look-up table 28 provides a scaling factor to beapplied to the input signal based on the measured average power. Outputscaler 30 applies the scaling factor to the equalized signal andsupplies the scaled signal to output 14. The scaling factor iscontinuously updated so as the level of the input signal changes so doesthe scaling factor. This provides for adaptively gain controlling thevoice signal. The default mode of voice enhancer 10 is to provide voiceenhancement to the voice signal.

Voice-band data detector 22 analyzes the input signal to determinewhether it includes voice-band data as opposed to a standard voicesignal. Bass to treble power comparator 20 measures the power ratio ofthe bass portion to the treble portion of the input signal to determineif the signal has been previously enhanced in the network. If eitherprevious enhancement or voice-band data is detected, then AGCenhancement disable 24 will cause switch 26 to decoupling the enhancedvoice signal from output 14.

Therefore, the AGC voice enhancement system of the present inventionprovides for adaptive gain control by applying a scaling factor to aninput voice signal and amplifying/attenuating the input voice signal toprovide a more representative signal of the speaker's voice at thereceiving telephone set. The present invention eliminates problemsassociated with prior fixed gain voice enhancement systems bycontinually and adaptively monitoring the input signal and appropriatelyscaling the input signal. Changes in the input signal are responded toso that when the input signal is received at the output receivingtelephone set, a truer representation of the input voice signal isobtained.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade hereto without departing from the spirit and scope of the inventionas defined by the appended claims.

What is claimed is:
 1. A method for providing voice enhancement in atelecommunications network, comprising the steps of:determining theaverage power of an input voice-band signal; determining a scalingfactor in response to the average power of the input voice-band signal;equalizing the input voice-band signal by attenuating a predeterminedportion of the input voice signal; scaling the equalized inputvoice-band signal with the scaling factor; coupling the scaledvoice-band signal to an output; and wherein said determining a scalingfactor step further comprises the step of limiting the amount of changebetween consecutive scaling factors.
 2. The method of claim 1 furthercomprising the steps of:detecting voice-band data in the input signal;and decoupling the scaled voice-band signal from the output.
 3. Themethod of claim 1 further comprising the steps of:detecting tandemenhancement in the network; and decoupling the scaled voice-band signalfrom the output.
 4. A method for providing voice enhancement in atelecommunications network, comprising the steps of:determining theaverage power of an input voice-band signal; determining a scalingfactor in response to the average power of the input voice-band signal;equalizing the input voice-band signal by attenuating a predeterminedportion of the input voice signal; scaling the equalized inputvoice-band signal with the scaling factor; coupling the scaledvoice-band signal to an output; detecting at least one of voice-banddata in the input signal and tandem enhancement in the network; anddecoupling the scaled voice-band signal from the output.
 5. The methodof claim 1 wherein said determining the average power, determining ascaling factor, equalizing, scaling, and coupling steps are performed inan echo canceller of a telecommunications network.
 6. The method ofclaim 1 wherein the predetermined portion of the input voice-band signalis above substantially 300 Hz.
 7. The method of claim 1 wherein thepredetermined portion of the input voice-band signal is abovesubstantially 400 Hz.
 8. The method of claim 1 wherein said scaling theinput signal step further comprises using the scaling factor for scalingthe equalized input signal for a predetermined period of time.
 9. Themethod of claim 1 further comprising the steps of:dividing the inputvoice-band signal into a plurality of frames, each frame representativeof a period of time; and scaling the equalized input signal with thescaling factor for a predetermined number of frames.
 10. The method ofclaim 1 wherein said equalizing step further comprises filtering theinput signal such that the power of the input signal above apredetermined frequency is attenuated.
 11. The method of claim 1 whereinsaid determining the average power step further comprises low passfiltering a rectified input voice-band signal.
 12. A method forproviding voice enhancement in a telecommunications network, comprisingthe steps of:determining the average power of an input voice-bandsignal; determining a scaling factor in response to the average power ofthe input voice-band signal; equalizing the input voice-band signal byattenuating a predetermined portion of the input voice signal; scalingthe equalized input voice-band signal with the scaling factor; couplingthe scaled voice-band signal to an output; comparing the determinedaverage power of the input voice-band signal to power measurementsexpected for a previously scaled signal; and decoupling the scaledvoice-band signal from the output in response to said comparing step.13. The method of claim 1 further comprising the steps of:dividing theinput voice-band signal into a plurality of frames, each framerepresentative of a period of time; continuously performing saiddetermining the average power, determining a scaling factor, equalizing,scaling, and coupling steps upon the expiration of a predeterminednumber of frames.
 14. A method for providing voice enhancement in atelecommunications network, comprising the steps of:determining theaverage power of an input voice-band signal; determining a scalingfactor in response to the average power of the input voice-band signal;equalizing the input voice-band signal by attenuating a predeterminedportion of the input voice signal; scaling the equalized inputvoice-band signal with the scaling factor coupling the scaled voice-bandsignal to an output; detecting periods of silence in the inputvoice-band signal at the input; and decoupling the scaled voice-bandsignal from the output.
 15. The method of claim 14 further comprisingthe step of attenuating the input voice-band signal so that the noiselevel of the detected periods of silence is minimized.
 16. A method forproviding voice enhancement in a telecommunications network, comprisingthe steps of:determining the average power of an input voice-bandsignal; determining a scaling factor in response to the average power ofthe input voice-band signal; equalizing the input voice-band signal byattenuating a predetermined portion of the input voice-band signal;scaling the equalized input voice-band signal with the scaling factor;coupling the scaled voice-band signal to an output; and detecting atleast one of voice-band data in the input signal and tandem enhancementin the network and decoupling the scaled voice-band signal from theoutput.
 17. The method of claim 16 wherein said determining the averagepower, determining a scaling factor, equalizing, scaling, and couplingsteps are performed in an echo canceller of a telecommunicationsnetwork.
 18. The method of claim 16 wherein the predetermined portion ofthe input voice-band signal is above substantially 300 Hz.
 19. (Amended)The method of claim 16 further comprising the steps of:dividing theinput voice-band signal into a plurality of frames, each framerepresentative of a period of time; and scaling the equalized inputsignal with the scaling factor for a predetermined number of frames. 20.The method of claim 16 further comprising the steps of:dividing theinput voice-band signal into a plurality of frames, each framerepresentative of a period of time; continuously performing saiddetermining the average power, determining a scaling factor, equalizingscaling and coupling steps upon the expiration of a predetermined numberof frames.
 21. The method of claim 16 further comprising the stepsof:detecting periods of silence in the input voice-band signal at theinput; and decoupling the scaled voice-band signal from the output. 22.The method of claim 21 further comprising the step of attenuating theinput voice-band signal so that the level of the detected periods ofsilence is minimized.
 23. A system for providing enhancement to avoice-band signal in a telecommunications network, comprising:a poweraverager for determining the average power of the voice-band signal; anequalizer for attenuating a predetermined portion of the voice-bandsignal; and an output scaler for scaling the equalized voice-band signalwith a scaling factor in response to the determined average power, andwherein said output scaler is further operable to limit the amount ofchange between consecutive scaling factors.
 24. The system of claim 23further comprising a voice-band data detector for detecting voice-banddata in the voice-band signal and preventing said output scaler fromscaling the voice-band signal.
 25. The system of claim 23 furthercomprising a tandem voice enhancement detector for detecting when thevoice-band signal has been previously scaled and preventing said outputscaler from scaling the voice-band signal.
 26. The system of claim 23further comprising:a voice-band data detector for detecting voice-banddata in the voice-band signal; a tandem voice enhancement detector fordetecting when the voice-band signal has been previously scaled; andwherein at least one of said voice-band data detector and said tandemvoice enhancement detector is operable to prevent said output scalerfrom scaling the voice-band signal.
 27. The system of claim 23 whereinsaid power averager, equalizer, and output scaler are located in an echocanceller of a telecommunications network.
 28. The system of claim 23wherein the predetermined portion of the voice-band signal attenuated bysaid equalizer is above substantially 300 Hz.
 29. The system of claim 23wherein the predetermined portion of the voice-band signal attenuated bysaid equalizer is above substantially 400 Hz.
 30. The system of claim 23wherein said output scaler is operable to scale equalized voice-bandsignals with a previously determined scaling factor for a predeterminedperiod of time.
 31. The system of claim 23 wherein said output scaler isfurther operable to divide the voice-band signal into a plurality offrames, each frame representative of a period of time, and to scale thevoice-band signal for a predetermined number of frames.
 32. The systemof claim 23 wherein said equalizer comprises a digital filter operableto filter the voice-band signal above a predetermined frequency.
 33. Thesystem of claim 23 wherein said power averager comprises a low passfilter.
 34. A system for providing enhancement to a voice-band signal ina telecommunications network, comprising:a power averager fordetermining the average power of the voice-band signal; an equalizer forattenuating a predetermined portion of the voice-band signal; an outputscaler for scaling the equalized voice-band signal with a scaling factorin response to the determined average power; and a gain/attenuationlook-up table for providing the scaling factor to be used by said outputscaler in scaling the voice-band signal.
 35. A system for providingenhancement to a voice-band signal in a telecommunications network,comprising:a power averager for determining the average power of thevoice-band signal; an equalizer for attenuating a predetermined portionof the voice-band signal; an output scaler for scaling the equalizedvoice-band signal with a scaling factor in response to the determinedaverage power; and a gain/attenuation look-up table for providing thescaling factor to be used by said output scaler in scaling thevoice-band signal, and wherein said gain/attenuation look-up table isorganized such that low power voice-band signals are assigned largescaling factors relative to high power voice-band signals, the highpower voice-band signals being assigned low or negative scaling factors.36. A system for providing enhancement to a voice-band signal in atelecommunications network, comprising:a power averager for determiningthe average power of the voice-band signal; an equalizer for attenuatinga predetermined portion of the voice-band signal; an output scaler forscaling the equalized voice-band signal with a scaling factor inresponse to the determined average power; a transparent path forproviding the input voice-band signal directly to an output so that theinput voice-band signal avoids scaling; and an attenuator coupled insaid transparent path for variably attenuating the input voice-bandsignal during periods of silence in the input voice-band signal.
 37. Asystem for providing enhancement to a voice-band signal in atelecommunications network, comprising:an input for accepting thevoice-band signal; an output for receiving the voice-band signal; and acoupling between said input and output including a voice enhancer, saidvoice enhancer comprising:a power averager for determining the averagepower of the voice-band signal; an equalizer for attenuating apredetermined portion of the voice-band signal; and an output scalercoupled to said output for scaling the equalized voice-band signal witha scaling factor in response to the determined average power andproviding the scaled signal to said output, and wherein said outputscaler is further operable to limit the amount of change betweenconsecutive sealing factors.
 38. The system of claim 37 furthercomprising a voice-band data detector for detecting voice-band data inthe voice-band signal and for decoupling said output scaler from saidoutput.
 39. The system of claim 37 further comprising a tandem voiceenhancement detector for detecting when the voice-band signal has beenpreviously scaled and for decoupling said output scaling circuitry fromsaid output.
 40. A system for providing enhancement to a voice-bandsignal in a telecommunications network, comprising:an input foraccepting the voice-band signal; an output for receiving the voice-bandsignal; and a coupling between said input and output including a voiceenhancer, said voice enhancer comprising:a power averager fordetermining the average power of the voice-band signal; an equalizer forattenuating a predetermined portion of the voice-band signal; an outputscaler coupled to said output for scaling the equalized voice-bandsignal with a scaling factor in response to the determined average powerand providing the scaled signal to said output; a voice-band datadetector for detecting voice-band data in the voice-band signal; atandem voice enhancement detector for detecting when the voice-bandsignal has been previously scaled; and wherein at least one of saidvoice-band data detector and said tandem voice enhancement detectorbeing operable to decouple said output scaler from said output.